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A2-class microSD cards offer no better performance for the Raspberry Pi

jeffgeerling.com

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Re: A2-class microSD cards offer no better performance for the Raspberry Pi

#21

Post by geerlingguy »

jacobush wrote: post #19
djsumdog wrote: post #18

I'm surprised we haven't seen a smaller than M.2 form factor for SATA on embedded devices. It seems like the big limiter on devices like the Raspberry Pi and others are the sd cards/emmc modules, since the amount processing power and ram have been continually going up. If you need disk performance on the Pi 4, wouldn't it make more sense to only keep the kernel,initrd on the sdcard and mount the primary filesystem of…

Yep. USB disks also are generally much more robust to errors than SD cards. My mail spool is on USB, the OS is on the SD card.

Soon (hopefully) the Pi 4 will be able to completely boot off USB 3.0 devices; right now you can partially boot off an external volume, but /boot still has to be on a microSD card.

Though in my testing, it's still not a night-and-day performance difference, if judged by the Pi 3B+. I am not sure if the Pi 4's USB 3.0 port bandwidth will give that much of an improvement.

It would be quite nice to have any form of drive supported more directly, NVMe, m.2, whatever.

Re: A2-class microSD cards offer no better performance for the Raspberry Pi

#22

Post by geerlingguy »

joshvm wrote: post #12
walrus01 wrote: post #3

The major problem is not disk write speed, which we can all agree sucks, but longevity and lifespan when used as a system boot disk and also containing /var and similar. The write wear leveling on a u3 microsd card is nowhere near as good as even a $50 consumer class ssd. Small single board computers should move towards m.2 2280 nvme drive support, or at least one sata 6 gbps interface.

SD card performance on the Pi Jeff's benchmarks are accurate in my experience. If you try saving single images from a camera at even 5-10fps, the card quickly bottleneck and you start dropping frames. If you buffer and store (in my case 16-bit raw), you can essentially saturate USB bandwidth if you're also using a USB camera.

Yeah I'm always fighting both write speed and network speed limitations when I do timelapse projects with my Pi Zeros. Hopefully the I/O improvements from the 4 trickle down to the Zero form factor sometime soon!

Re: A2-class microSD cards offer no better performance for the Raspberry Pi

#23

Post by NikolaeVarius »

geerlingguy wrote: post #21
jacobush wrote: post #19

Earlier quoted context omitted.

Yep. USB disks also are generally much more robust to errors than SD cards. My mail spool is on USB, the OS is on the SD card.

Soon (hopefully) the Pi 4 will be able to completely boot off USB 3.0 devices; right now you can partially boot off an external volume, but /boot still has to be on a microSD card. Though in my testing, it's still not a night-and-day performance difference, if judged by the Pi 3B+. I am not sure if the Pi 4's USB 3.0 port bandwidth will give that much of an improvement. It would be quite nice to have any form of driv…

Does /boot get read/written to enough where this is not "good enough"

Re: A2-class microSD cards offer no better performance for the Raspberry Pi

#24

Post by mrb »

walrus01 wrote: post #3

The major problem is not disk write speed, which we can all agree sucks, but longevity and lifespan when used as a system boot disk and also containing /var and similar. The write wear leveling on a u3 microsd card is nowhere near as good as even a $50 consumer class ssd. Small single board computers should move towards m.2 2280 nvme drive support, or at least one sata 6 gbps interface.

There are SD cards rated for "high endurance" for example https://www.amazon.com/gp/aw/d/B07B984HJ5 is designed for continuous 24/7 writes such as surveillance cameras. These should have great longevity when used in a RPi.

What I would really like to see is RPi configurations optimized to reduce writes. For example mount the whole SD card read-only, mount a few essential filesystems as ramfs (/var, /tmp, /run), and have, say only one partition like /srv mounted read-write (+ noatime). If you run a webserver, and serve files off /srv you can still update them whenever with no hassle, but when the webserver is otherwise just serving the files, there should be zero writes.

Re: A2-class microSD cards offer no better performance for the Raspberry Pi

#25

Post by geerlingguy »

jdietrich wrote: post #20
djsumdog wrote: post #18

I'm surprised we haven't seen a smaller than M.2 form factor for SATA on embedded devices. It seems like the big limiter on devices like the Raspberry Pi and others are the sd cards/emmc modules, since the amount processing power and ram have been continually going up. If you need disk performance on the Pi 4, wouldn't it make more sense to only keep the kernel,initrd on the sdcard and mount the primary filesystem of…

The SD 7.0 standard includes support for PCIe and NVMe. https://www.sdcard.org/press/SD_EXPRESS_A_REVOLUTIONARY_INNO...

Good chance that doesn't trickle down to the microSD interface; it seems like the best performance improvements are reserved for the full-size SD cards, likely because they can fit more thermal mass and connection pins in the larger case.

Re: A2-class microSD cards offer no better performance for the Raspberry Pi

#26

Post by sgt »

joshvm wrote: post #12
walrus01 wrote: post #3

The major problem is not disk write speed, which we can all agree sucks, but longevity and lifespan when used as a system boot disk and also containing /var and similar. The write wear leveling on a u3 microsd card is nowhere near as good as even a $50 consumer class ssd. Small single board computers should move towards m.2 2280 nvme drive support, or at least one sata 6 gbps interface.

SD card performance on the Pi Jeff's benchmarks are accurate in my experience. If you try saving single images from a camera at even 5-10fps, the card quickly bottleneck and you start dropping frames. If you buffer and store (in my case 16-bit raw), you can essentially saturate USB bandwidth if you're also using a USB camera.

We've got a few Pi's in office "production" (used as dashboards) and the best solution we've found it to use an SSD drive via USB. Something like a 128GB SSD drive is cheap enough, although it's about as expensive as the Pi itself.

Re: A2-class microSD cards offer no better performance for the Raspberry Pi

#27

Post by m-p-3 »

walrus01 wrote: post #3

The major problem is not disk write speed, which we can all agree sucks, but longevity and lifespan when used as a system boot disk and also containing /var and similar. The write wear leveling on a u3 microsd card is nowhere near as good as even a $50 consumer class ssd. Small single board computers should move towards m.2 2280 nvme drive support, or at least one sata 6 gbps interface.

Or at least support USB boot out-of-the-box. At lease someone could buy a USB 3.1 M.2 enclosure and boot from that if they need the stability and speed without modifying the form-factor or increasing the price.

Re: A2-class microSD cards offer no better performance for the Raspberry Pi

#28

Post by patentatt »

pingec wrote: post #9
walrus01 wrote: post #3

The major problem is not disk write speed, which we can all agree sucks, but longevity and lifespan when used as a system boot disk and also containing /var and similar. The write wear leveling on a u3 microsd card is nowhere near as good as even a $50 consumer class ssd. Small single board computers should move towards m.2 2280 nvme drive support, or at least one sata 6 gbps interface.

Exactly, who cares about speed when all the microSD cards I try eventually become corrupt due to poor controller logic.

Try an ‘industrial’ flash card. I outfitted my pi with a SwissBit microsd and haven’t had any disk problems since.

Re: A2-class microSD cards offer no better performance for the Raspberry Pi

#29

Post by geerlingguy »

NikolaeVarius wrote: post #23
geerlingguy wrote: post #21

Earlier quoted context omitted.

Soon (hopefully) the Pi 4 will be able to completely boot off USB 3.0 devices; right now you can partially boot off an external volume, but /boot still has to be on a microSD card. Though in my testing, it's still not a night-and-day performance difference, if judged by the Pi 3B+. I am not sure if the Pi 4's USB 3.0 port bandwidth will give that much of an improvement. It would be quite nice to have any form of driv…

Does /boot get read/written to enough where this is not "good enough"

It doesn't, but in my informal tests (I haven't had time to set up a thorough benchmark) real-world usage of an external USB 3.0 SSD (testing with a cheap Kingston SSD, though, and a cheap USB SATA interface) is only marginally faster than a Samsung Evo+ microSD card.

Re: A2-class microSD cards offer no better performance for the Raspberry Pi

#30

Post by jws »

geerlingguy wrote: post #25
jdietrich wrote: post #20

Earlier quoted context omitted.

The SD 7.0 standard includes support for PCIe and NVMe. https://www.sdcard.org/press/SD_EXPRESS_A_REVOLUTIONARY_INNO...

Good chance that doesn't trickle down to the microSD interface; it seems like the best performance improvements are reserved for the full-size SD cards, likely because they can fit more thermal mass and connection pins in the larger case.

The term you want is “microSD express”. That is the standard for PCIe and NVME on microSD cards. It specs out at about 1GB/second transfer rates.

Fun engineering decisions: It can use RAM from the hosting computer to store its logical block mapping tables so it doesn’t have to have DRAM onboard for that. That’s a clever way to use what the host has in abundance to avoid putting it on the price and volume constrained microSD card.

Now… how you are going to get the heat out of it when it is running at 1GB/sec. I wonder if we will see new microSD sockets with integrated heat sinks.

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